Oxygen activation on Cu/Mn-Ce mixed oxides and the role in diesel soot oxidation

The Cu- and Mn-doped ceria were prepared using the citric acid sol-gel method. The structural and redox properties of the mixed oxides were investigated by means of XRD, BET, O-2-TPD, CO-TPR and CO reduction under isothermal conditions. TPO tests were performed to evaluate the catalytic activity for soot oxidation. The results showed that Mnx+ cations entered into the ceria lattice to form solid solutions, which increased the amount of oxygen vacancies and promoted surface oxygen chemisorption. CuxO clusters were more likely to be dispersed on the surface of ceria particles. The interaction between copper and cerium greatly enhanced the rapid release of lattice oxygen of the oxides in the reducing atmosphere. These two mixed oxides showed improved catalytic activities and selectivities to CO2 for soot oxidation compared with pure ceria. The order of activities under different contact conditions was believed to be related to active oxygen species released by the catalysts. (C) 2008 Elsevier B.V. All rights reserved.